A mixed chemical (mixed acid) including a phosphoric acid and a nitric acid may be used in a process of removing (etching) a metallic film formed on a surface of a substrate such as a semiconductor wafer (hereinafter briefly referred to as a “wafer”).
Recently, in response to higher integration in semiconductor devices, development has been shifted to a new device in which a stack film formed on a wafer is three-dimensionally processed from a conventional device having a two-dimensional planar structure. In such a device, the use of a process with the mixed acid is considered for the wet etching of the metallic film of the stack film.
However, films slightly insoluble in acids such as a metallic film including tungsten have the problem of the deterioration of etching characteristics.